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The present invention relates to a vehicular lamp employing a plurality of LED light sources and, more particularly, to a vehicular lamp which radiates light using an indirect illumination technique.
Many vehicular lamps that have been employed in recent years are equipped with LED light sources. For example, Japanese Patent Application Laid-Open No. 11-306810 discloses a lamp having LED light sources disposed so as to be invisible from the front of the lamp, thus providing a soft lighting effect due to the use of an indirect illumination technique. Further, as disclosed in German Patent Application Laid-Open No. 19638081, some vehicular lamps of an indirect illumination type are equipped with Fresnel lenses as well as LED light sources.
FIG. 9 is a front view of a vehicular lamp 100 of such a type. As shown in the drawing, in the vehicular lamp 100 light emitted by a plurality of LED light sources 102 disposed facing upward is formed into parallel light beams by a plurality of Fresnel lenses 104 disposed above the LED light sources 102, and a reflector 106 reflects the parallel light beams from the Fresnel lenses 104 in the directly forward direction of the lamp. The light emitted by the light sources thus can be effectively utilized by combining the LED light sources 102 with the Fresnel lenses 104.
The reflector 106 of the vehicular lamp 100 is divided into smaller sub reflectors 108 disposed in the areas where the parallel light beams from the Fresnel lenses 104 impinge, and the sub reflectors 108 are made different in height so as to conform to the contour of the lamp. In order to ensure that the parallel light beams from each of the Fresnel lenses 104 impinges on a reflecting surface 108a of a corresponding one of the sub reflectors 108, the sub reflectors 108 are designed such that the angle of inclination in the directly forward direction of the lamp increases as the height of the sub reflectors 108 decreases.
However, the aforementioned conventional vehicular lamp 100 lacks a desired visual impressiveness when lighted.
That is, as shown in FIG. 10, the vehicular lamp 100 is designed such that the sub reflectors 108 and the Fresnel lenses 104 are all equal in lateral width (P1xe2x80x2=P2xe2x80x2=P3xe2x80x2=P4xe2x80x2=P5xe2x80x2). The LED light sources 102 are all spaced from corresponding ones of the Fresnel lenses 104 by an equal distance Hxe2x80x2. Thus, the luminous fluxes impinging on each of the Fresnel lenses 104 from corresponding ones of the LED light sources 102 have equal intensities (F1xe2x80x2=F2xe2x80x2=F3xe2x80x2=F4xe2x80x2=F5xe2x80x2). On the other hand, since the sub reflectors 108 differ in projected area in the forward direction of the lamp (A1xe2x80x2 less than A2xe2x80x2 less than A3xe2x80x2 less than A4xe2x80x2 less than A5xe2x80x2), the reflecting surfaces 108a of the sub reflectors 108 increase in luminance and appear brighter as the aforementioned projected areas become smaller in size.
More specifically, the reflecting surface 108a of each of the sub reflectors 108 is vertically divided into a plurality of segments so as to form the sub reflector in a stepped manner. Each segment contains a reflecting element 108s for diffusively reflecting the parallel light flux from a corresponding one of the Fresnel lenses 104 in the directly forward direction of the lamp and a vertically extending step portion 108r. Hence, if the reflector 106 is observed from the front of the lamp when the lamp is lighted, central portions of the reflecting elements 108s appear bright as glitter portions Bxe2x80x2.
The glitter portions Bxe2x80x2 appear substantially equally bright among the reflecting elements 108s and among the sub reflectors 108. However, the vertical distance among the reflecting elements 108s constituting each of the sub reflectors 108 decreases in proportion to a decrease in the aforementioned projected area. Hence, if the sub reflectors 108 are observed one by one, they increase in luminance and look brighter in proportion to the decrease in the aforementioned projected area.
Hence, it is impossible to make the entire reflecting surface of the reflector 106 look substantially homogeneous in brightness, which adversely affects the appearance of the lamp when the lamp is lighted.
The present invention has been made in consideration of such circumstances. It is an object of the present invention to provide a vehicular lamp that radiates light emitted from a plurality of LED light sources through indirect illumination and which has an improved appearance when lighted.
The present invention achieves the above and other objects with a vehicular lamp having a controlled positional relationship between each of LED light sources and corresponding ones of the lenses.
More specifically, a vehicular lamp according to the present invention comprises a plurality of LED light sources, a plurality of lenses for forming parallel light beams from the light from the LED light sources, a reflector for reflecting the parallel light beams from the lenses in the directly forward direction of the lamp, and a translucent cover disposed in front of the reflector with respect to the lamp. The lenses are disposed such that the parallel light beams travel in the same direction, the reflector is divided into sub reflectors according to areas on which the parallel light beams from the lenses impinge, the sub reflectors differ in length with respect to the direction of radiation of the parallel light beams and are designed such that the angle of inclination in the directly forward direction of the lamp increases in proportion to the decrease in the length of the sub reflectors in the direction of radiation of the parallel light beams, and the distance between each of the LED light sources and the corresponding one of the lenses increases in proportion to the decrease in the length of the sub reflector in the direction of radiation of the parallel light beams.
The lenses are not specifically limited in construction as long as they can form parallel light beams from the light emitted by the LED light sources. For instance, single spherical lenses, combinational lenses, Fresnel lenses, and the like can be adopted.
Also, the directions of the parallel light beams are not specifically limited as long as they intersect the longitudinal direction of the lamp. For instance, the parallel light beams can be directed upward or transversely while being perpendicular to the longitudinal direction of the lamp.
The reflector may be integrally formed of a plurality of sub reflectors or be formed of separated sub reflectors.
The sub reflectors are not specifically limited in shape, size, or the like as long as they differ in length with respect to the direction of radiation of the parallel light beams and as long as they are designed such that the angle of inclination in the directly forward direction of the lamp increases in proportion to the decrease in the length in the direction of radiation of the parallel light beams. It is not absolutely required that all the sub reflectors are different in length with respect to the direction of radiation of the parallel light beams. It is appropriate that at least two of the sub reflectors be different in length with respect to the direction of radiation of the parallel light beams.
As is apparent from the description above, the vehicular lamp according to the present invention is designed such that the lenses for forming parallel light beams from light from the LED light sources are disposed so as to direct the parallel light beams in the same direction, the reflector for reflecting the parallel light beams from the lenses in the directly forward direction of the lamp is divided into sub reflectors according to the areas impinged by the parallel light beams from the lenses, the sub reflectors differ in length with respect to the direction of radiation of the parallel light beams, the sub reflectors are formed such that the angle of inclination increases in the directly forward direction of the lamp in proportion to the decrease in the length in the direction of radiation of the parallel light beams, and the sub reflectors are formed such that the distance between each of the LED light sources and the corresponding one of the lenses increases in proportion to the decrease in the length of the sub reflector in the direction of radiation of the parallel light beams. With this construction, the following effects can be achieved.
That is, since the sub reflectors differ in length with respect to the direction of radiation of the parallel light beams and are designed such that the angle of inclination toward the region in front of the lamp increases in proportion to a decrease in the length, the sub reflectors differ in projected area in the direction extending forward of the lamp. Hence, if each of the LED light sources is equally distant from a corresponding one of the lenses, the sub reflectors increase in luminance and look brighter in proportion to the decrease in the aforementioned projected area.
On the other hand, according to the present invention, the sub reflectors are designed such that the distance between each of the LED light sources and a corresponding one of the lenses increases in proportion to the decrease in the length of a corresponding one of sub reflectors in the direction of radiation of the parallel light beams, whereby the sub reflectors can be designed such that the luminous flux impinging on each of the lenses from a corresponding one of the LED light sources decreases in proportion to the decrease in length of a corresponding one of the sub reflectors in the direction of radiation of the parallel light beams. Hence, the sub reflectors exhibit the same luminance when the lamp is lighted, and the entire reflecting surface of the reflector can be made to appear substantially homogeneous in brightness.
Accordingly, the present invention makes it possible to improve the appearance of a vehicular lamp which radiates light from a plurality of LED light sources through indirect illumination when the lamp is lighted.
The sub reflectors and the lenses may be equal or different in width in the direction perpendicular to the longitudinal direction of the lamp. In the former case, light emitted from an LED light source spaced from the corresponding lens by a relatively great distance partially fails to impinge on that lens and is wasted. In the latter case, however, if the sub reflectors and the corresponding lenses are designed such that the width in the direction perpendicular to the longitudinal direction of the lamp increases in proportion to the decrease in the length of the sub reflector in the direction of radiation of the parallel light beams, the sub reflectors appear uniform in luminance while substantially all the light emitted from each of the LED light sources is guaranteed to impinge on one of the lenses without waste.
The reflecting surface of each of the sub reflectors may be constructed of a single curved surface or of a plurality of reflecting elements. In the latter case, if the reflecting surface of each of the sub reflectors is divided into a plurality of segments with respect to the direction of radiation of the parallel light beams and is formed in a stepped manner with one of the reflecting elements and a corresponding one of step portions being provided in each of the segments, the available light can be efficiently radiated in the directly forward direction of the lamp. It is also appropriate for the reflecting surface of each of the sub reflectors to be divided into a plurality of segments with respect to the direction perpendicular to the longitudinal direction of the lamp.
If each of the reflecting elements is constructed of a curved surface for diffusively reflecting parallel light beams from a corresponding one of the lenses vertically and laterally, the lamp will exhibit the desired light distribution performance even in the case where the translucent cover is formed as a transparent type.
Alternatively, it is also possible to construct each of the reflecting elements as a flat surface so that the parallel light beams from the lenses are reflected as they are, that is, parallel in the directly forward direction of the lamp, while forming diffusion lens elements on the translucent cover or the like to diffuse the light beams vertically and laterally. It is also possible to construct each of the reflecting elements as a surface curved in only one direction so that the parallel light beams from the lenses are diffusively reflected in only one direction, while forming diffusion lens elements on the translucent cover or the like to diffuse the light beams in the direction perpendicular to the aforementioned one direction.